MODELS

Stopped car at a red light on hot day after driving on highway. After a few seconds, engine suddenly stalled as if it was choking. It started right up and I drove home. &Quot; Service Engine Soon" light came on and there were a few short periods of engine roughness at highway speed. Stalled a few more times at traffic lights, after about 10 seconds of idling, but started right up each time.

At home, checked the OBD code: it was 34. Checked all hoses and electrical connections. Tried running with air filter removed: still stalls. Tried again when engine was cold: problem appears to be gone but I'm afraid it will come back when engine is hot.

MAP sensor (high vaccum) error. Check the vaccum hose to MAP and electrical connection (sounds like you already have).
The MAP error will cause the cause the car to stall, or barely run (rich).
Make sure the hose that goes to the MAP is not cracked or clogged before you replace it. Also make sure the connector (locking tang) is not broken.
Replace MAP sensor, disconnect the negative battery cable for a minute or two to clear the code.

I got a used MAF sensor. No change. But who knows if the used one is any good.

But in the meantime I did a little science project. I disconnected the wires from the MAF sensor. The car runs fine, even when warmed up! No stalling! (I'm getting code 34 of course.)

Who knows if the acceleration is still the same, or the gas mileage, or if the emissions are correct. But no stalling! And state emissions inspection is 16 months away.

I think what is happening is that the computer uses two inputs to decide on how much gas to inject: the throttle position and the MAF reading. When the MAF sensor is disconnected, it just uses the throttle position as a first approximation, which works better than using garbage results from a bad MAF sensor.

Next research question: what is the gas mileage with the MAF sensor disconnected? Stay tuned.

Running with the MAF disconnected worked well for a while, but then it went back to stalling.

Got a used MAF. There was no change in the car's stalling. Using an ohm meter, I measured something like 50 megohms between each pair of pins. Same thing on both the old MAF and the replacement.

Finally I got another used MAF, and it fixed the stalling problem. This good one had much lower resistance between the pins marked + and -. About 6 K Ohms in one polarity and about 500 K Ohms with the probes reversed. The other pin had much higher resistance.